1. Field of the Invention
This invention relates to an opening and closing mechanism for the seat and cover which are provided on a stool.
2. Description of the Prior Art
For a flush toilet, a seat only or a seat with a closable cover is generally mounted, and that with the base end portion coupled to a stool body by a hinge mechanism is employed as the simplest structure.
The hinge mechanism consists of base end portions of the seat and cover connected to the stool body by a shaft such as pins or the like, and the seat and cover are coupled integrally or rotatably with the pins, thus rotating freely to a hinge part of the stool body.
However, in such a seat and cover working on a free rotation system, the seat and cover naturally fall shut when unhanded and thus cause a loud sound when striking the stool body; therefore care should particularly be taken when using it at night. Further, frequent shocks resulting on the stool body by the seat and cover may cause the hinge part to work loose, thus shortening the life of the product.
To solve such problems, there is provided a structure operating slowly by loading a rotation of the seat and cover on the hinge mechanism with a resistance.
For example, a structure wherein a coil spring is provided around a shaft of the hinge mechanism is disclosed in the specification and drawings of Japanese Utility Model Application No. 188910/1985, and thus if unhanded halfway before closing the seat and cover, the sudden fall is damped by the resilience of the coil spring, thus relieving the shock to the stool body. And, also, an opening and closing mechanism using a viscous damper or the like as the resisting means to the rotation of the hinge shaft has also been proposed.
However, the moment of rotational force about the hinge is slight immediately after the seat and cover start the inclination from the erected state, but increases with the angle toward the stool body, the torque working on the hinge changes, and the torque is maximized immediately before completely closing.
In the aforementioned structure wherein a rotation of the hinge mechanism is loaded with a resistance, the resistance works almost with a constant force to the operation of the seat and cover from the erected state to closing.
Thus, if a resistance value by rotation resisting means provided on the hinge mechanism is smaller than the maximum torque generated by the seat and cover, the damping capacity to the shock substantially becomes zero. Further, for the damping capacity to function, if the resistance value is given so as to be equal to the maximum torque or greater than that, the rotation resistance form erected state to closing increases excessively and the time is prolonged, which is not practical.
If a viscous damper is employed as a rotation resisting means for the hinge, it also works as a resistance at the time when the seat and cover are erected, thus requiring a large force compared with a conventional free rotation type.
To solve the aforementioned problem, it is effective to provide an opening and closing mechanism having a variable torque function capable of coping with a torque change about the hinge. However, a variable torque device employed as an opening and closing mechanism for the seat and cover in the prior art is complicated in structure and large in addition. Consequently, such a particular type as is enclosed in a casing such as a sanitary washing device or the like which is ancillary to the stool body is not acceptable particularly for installation.
Further, the defect is such that hinge mechanism for rotation of the seat and cover in the prior art requires excessive space, and where it is applied to the stool provided with a sanitary device for washing the private parts which is used extensively of late, another auxiliary mechanism or, for example, a mechanism for retaining an erected posture of the seat and cover can no more be provided.